Consider to add new option for zabbix_sender.exe and other platforms zabbix_sender

--use-config - use zabbix_agent config

if --use-config is used without -c then zabbix_agentd.conf is searched using config default location.

For example:

zabbix_sender.exe -s host -k key -o value  .... --use-config

It's not such a big problem to provide /etc/zabbix/zabbix_agentd.conf on Linux, but paths are quite long when used on Windows (with zabbix_sender.exe). That where it would benefit the most with proper default.

P.S. As an alternative to --use-config, just provide --config without any value

zabbix_sender.exe -s host -k key -o value  .... --config